> On 14.06.21 15:23, Claudio Imbrenda wrote:
> > Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added
> > support for hugepage vmalloc mappings, it also added the flag
> > VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to
> > be performed with 0-order non-huge pages. This flag is not accessible
> > when calling vmalloc, the only option is to call directly
> > __vmalloc_node_range, which is not exported.
> >
> > This means that a module can't vmalloc memory with small pages.
> >
> > Case in point: KVM on s390x needs to vmalloc a large area, and it needs
> > to be mapped with non-huge pages, because of a hardware limitation.
> >
> > This patch adds the function vmalloc_no_huge, which works like vmalloc,
> > but it is guaranteed to always back the mapping using small pages. This
> > new function is exported, therefore it is usable by modules.
> >
> > Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> > Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> > Acked-by: Nicholas Piggin <npiggin@xxxxxxxxx>
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
> > Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: David Rientjes <rientjes@xxxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > ---
> > include/linux/vmalloc.h | 1 +
> > mm/vmalloc.c | 16 ++++++++++++++++
> > 2 files changed, 17 insertions(+)
> >
> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index 4d668abb6391..bfaaf0b6fa76 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/include/linux/vmalloc.h
> > @@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
> > const void *caller);
> > void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
> > int node, const void *caller);
> > +void *vmalloc_no_huge(unsigned long size);
> > extern void vfree(const void *addr);
> > extern void vfree_atomic(const void *addr);
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index a13ac524f6ff..296a2fcc3fbe 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2998,6 +2998,22 @@ void *vmalloc(unsigned long size)
> > }
> > EXPORT_SYMBOL(vmalloc);
> > +/**
> > + * vmalloc_no_huge - allocate virtually contiguous memory using small pages
> > + * @size: allocation size
> > + *
> > + * Allocate enough non-huge pages to cover @size from the page level
> > + * allocator and map them into contiguous kernel virtual space.
> > + *
> > + * Return: pointer to the allocated memory or %NULL on error
> > + */
> > +void *vmalloc_no_huge(unsigned long size)
> > +{
> > + return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL,
> > + VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0));
> > +}
> > +EXPORT_SYMBOL(vmalloc_no_huge);
> > +
> > /**
> > * vzalloc - allocate virtually contiguous memory with zero fill
> > * @size: allocation size
> >
>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
>
>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
--
Vlad Rezki
